The United States Department of Energy (DOE) estimates that in 2015, light-emitting diode (LED)-based lamps comprised just 6.4% of the U.S. installed base. Despite this low level of adoption so far, most forecasts project extraordinary growth of SSL technology over the next 5 to 10 years. Lighting industry forecasters predict that SSL will become the dominant lighting technology in the total amount of artificial light generated, the revenue from sales, and the number of installed units. However, the DOE notes that the industry must overcome several significant challenges before solid state lighting can become the dominant lighting technology.
These remaining challenges include ongoing efficiency improvement, continued price reduction, manufacturing scale-up, and effective building integration and installation. Additionally, SSL will need to incorporate new value and features such as controls and connectivity that can provide further energy savings and accelerate adoption. Addressing these challenges can help the United States secure a dominant role in the technology and manufacturing of SSL products.
In the U.S. by 2030, LED lighting is predicted to account for the majority of lighting installations and represent 88 percent of the lumen-hours that general illumination produces. The DOE cites the high efficacy of SSL as a critical factor in the drive for higher adoption. Notably, LED lighting already can be more efficient than all incumbent technologies, but the DOE says that there is still room to improve LED efficiency.
Even with relatively conservative projections for performance improvements, the DOE has projects that by 2030, LED technology can potentially save as much as 261 terawatt-hours (TWh) annually, a 40% reduction of the site electricity consumption forecasted compared to a “no-LED” lighting scenario.
If these more aggressive performance improvements that the DOE is targeting can be reached through continuing investment in R&D, the total annual savings could increase to 395 TWh by 2030, a 60% reduction of the site electricity consumption for lighting. This energy savings amounts to nearly twice the projected electricity generation of wind power and 20 times that of solar power in 2030. At an average commercial price of $0.10/kilowatt-hour, 395 TWh this would correspond to an annual dollar savings of about $40 billion. Substantial and continued improvements in both efficacy and pricing are needed to reach these performance benchmarks, according to the DOE.
DOE says its support is essential to achieving the greater than 200 lumens per watt (lm/W) luminaire efficacy program goal by 2025 in addition to reducing SSL manufacturing costs, and realizing huge energy savings. DOE advocates continued focus on R&D to achieve these goals.
The DOE developed the latest R&D Plan in conjunction with community experts through input from roundtable meetings held in September and October 2015 and from the DOE SSL R&D Workshop, in February 2016 in Raleigh, NC. The DOE R&D plan reflects SSL stakeholder input on key R&D issues such as improving efficacy, reducing cost,and adding value of SSL solutions, and removing barriers to adoption over the next 3 to 5 years.
Advances in efficiency and costs in LED lighting has reduced payback periods of some products to as few as two years. However, according to the DOE’s R&D roadmap, improvements in LED package efficacy are becoming harder to achieve. Therefore, R&D is required to address technological barriers such as the efficiency gap of green
LEDs, current efficiency droop, and the need to develop new high-efficiency, narrow linewidth down-converter materials.
While SSL sources are inherently dimmable, the integration of sophisticated ICs is required to work with standard light dimmers. Luminaires can be integrated with occupancy sensing, daylight harvesting, and local control of light levels for further energy savings potential. The high-speed modulation capability of semiconductor light sources has enabled new features such as indoor positioning capabilities.
SSL offers can potentially enable the full-color control over the light spectrum while reducing glare, reducing stray light, and optimize useful light. This level of control enables applications in areas as diverse as human health and horticulture. Also, high-speed modulation can even enable visible light communication. With these and other new applications, the DOE predicts that SSL will expand the concept of what lighting can do.
Similarly, OLEDs offer a whole new approach with low luminance, thin profile, and the potential for surface shaping. OLED pricing has been static over the last year. OLED producers released few new panel models and products in 2015. LED technology has become a moving target for OLED products in performance and pricing. However, OLED makers are optimistic that advancements in light extraction and manufacturing yield, can allow OLEDs to offer a complementary value proposition to LED lighting.
Stakeholders identified key challenges facing the industry at the DOE roundtable meetings and workshops. The DOE selected these technological challenges to be LED-Based Lighting R&D priorities.
LED Lighting R&D Priorities
- Improvements in emitter materials should address current density and thermal droop, green and red efficiency, and red thermal stability.
- The industry should develop more efficient, stable, narrow linewidth down converter materials such as phosphors.
- Scientists should gain a better understand of the human, animal and plant responses to light so that the industry can develop lighting products that save energy while improving well-being, increasing productivity, and minimizing negative impacts of artificial lighting.
- The performance of encapsulation materials needs to be improved to increase LED package efficiency, increase light output, and expand the range of operating temperature.
- Power supplies need to be made more efficient and robust with minimized flicker across the operating range of the luminaire.
- Light designers need to develop advanced luminaire concepts that increase efficacy and add value for specific lighting applications.
- The industry needs to develop manufacturing approaches that can help simplify manufacturing for a broader range of luminaire products.
The DOE also outlined R&D priorities for OLED lighting based on stakeholder input.
OLED R&D Lighting Priorities
- OLED materials need to attain both long lifetimes and high efficiency, particularly for blue emitters where performance is lagging.
- OLED makers need to develop cost-effective, manufacturable solutions that will substantially improve panel efficiency by extracting light trapped in organic/anode wave-guided modes and reducing surface plasmonic losses.
- OLED makers need to develop new OLED-base luminaires to help
accelerating the marketability of OLED lighting through
product differentiation, integrability, ease of installation.
- One of the keys to improving OLED technology is to Improve the yield and reliability of OLED manufacturing methods. DOE suggests that OLED makers should be better able to fabricate OLEDs on flexible substrates for applications such as conformable OLED lighting. This might be achieved through the use of roll-to-roll (R2R) manufacturing of OLED material.